15 

 Understanding of the nutritional and metabolic roles of 

 Cu is based on the functions of the known Cu-enzymes and on 

 its role in disulfide bonding of keratin by an unknown 

 mechanism; however, knowledge of its biological roles remains 

 incomplete (Danks, 1988) . In animals there are approximately 

 ten proteins that are generally accepted as true cuproenzymes 

 (Prohaska, 1988) . In addition to the known cuproenzymes with 

 specific functions, there are about 12 proteins of unknown 

 functions that when isolated contain one or more Cu atoms 

 (Prohaska, 1988) . Some of the ten known cuproenzymes include: 

 1) tyrosinase (formation of melanin); 2) lysil oxidase 

 (synthesis of structural subunits of collagen and elastin) ; 3) 

 dopamine S-hydroxylase (adrenal synthesis of catecholamine; 4) 

 superoxide dismutase (immune, antioxidant function); 5) 

 cytochrome C oxidase (energy metabolism via oxidative 

 phosphorylation) (Allen and Solomons, 1984) . Copper has also 

 been suggested in the mineralization of growing bone, either 

 in a cuproenzyme with ascorbate oxidase activity, or in its 

 soluble ionic form (Hsieh and Hsu, 1980) . A great deal of 

 current research on Cu metabolism is focused on the use of Cu 

 to improve immune response. 



Absorption 



In monogastrics , Cu is absorbed from all segments of the 

 gastrointestinal tract including stomach and large intestine 

 (Mason, 1979; Davis and Mertz, 1986). The major site of Cu 



